This invention relates to an internal combustion engine and more particularly to an improved lubricating system for the valve actuating mechanism of such engines.
In four cycle internal combustion engines, the valves are normally operated by means of a cam shaft that rotates about an axis and is driven by the crankshaft at one-half crankshaft speed. The cam shaft has individual lobes that engage some form of follower mechanism for actuating the valves either directly or via an intermediate mechanism such as tappets, push rods and rocker arms. As is well known, the operating load on the valve actuating mechanism is particularly high especially in the area where the cam lobe contacts the valve actuating follower.
It has been the practice, therefore, to provide adequate lubrication in this area by drilling the cam shaft and cross drilling the cam lobe so that lubricant can be delivered to its surface and to the follower which they engage. Although this type of lubrication system is quite advantageous, it has some disadvantages, particularly with some types of applications.
Obviously, when the cam lobe is rotating and the opening is not engaged with the follower, the lubricating opening of the cam lobe is not adjacent the surfaces to be lubricated. Thus substantial oil will flow out of the opening which must be recaptured and recirculated. This also tends to reduce the pressure in the system and thus, higher pressures must be employed in order to compensate for this pressure loss.
In addition, it is not particularly desirable to drill holes for lubricating purposes through a surface of the cam lobe which functions to engage another member. The edges of such holes can cause scuffing action on the engaged follower.
It is, therefore, a principal object of this invention to provide an improved lubricating system for the cam lobe surfaces and engaged follower of the valve actuating mechanism for an engine.
It is a further object of this invention to provide a lubricating system for the cam lobes and follower of an engine wherein the lubricant is directed primarily to the surfaces that require it.
Frequently, the engine employs a plurality of cam shafts and this further aggravates the problem of providing adequate lubricating. That is, if each cam shaft is lubricated in the prior art type as described, then the problems become somewhat compounded and the amount of machining is significantly increased.
It is, therefore, a further object of this invention to provide an improved arrangement for lubricating a pair of cam shafts that are juxtaposed to each other and their associated follower mechanisms.